# Conway's Game of Life

We'll include just the main widget from Life; there are also a rudimentary main() and a dialog which wraps this widget in a QSlider to set the speed as well as Pause and Quit buttons. . The class definition:

    /****************************************************************************
    ** $Id: life.h,v 2.2 1998/05/21 19:24:54 agulbra Exp $
    **
    ** Copyright (C) 1992-1998 Troll Tech AS.  All rights reserved.
    **
    ** This file is part of an example program for Qt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #ifndef LIFE_H
    #define LIFE_H

    #include <qframe.h>

    class LifeWidget : public QFrame
    {
        Q_OBJECT
    public:
        LifeWidget( QWidget *parent = 0, const char *name = 0 );

        void        setPoint( int i, int j );

        int         maxCol() { return maxi; }
        int         maxRow() { return maxj; }

    public slots:
        void        nextGeneration();
        void        clear();

    protected:
        virtual void paintEvent( QPaintEvent * );
        virtual void mouseMoveEvent( QMouseEvent * );
        virtual void mousePressEvent( QMouseEvent * );
        virtual void resizeEvent( QResizeEvent * );
        void         mouseHandle( const QPoint &pos );

    private:
        enum { SCALE = 10, MAXSIZE = 50, MINSIZE = 10, BORDER = 5 };

        bool        cells[2][MAXSIZE + 2][MAXSIZE + 2];
        int         current;
        int         maxi, maxj;

        static int pos2index( int x )
        {
            return ( x - BORDER ) / SCALE + 1;
        }
        static int index2pos( int i )
        {
            return  ( i - 1 ) * SCALE + BORDER;
        }

    };

    #endif // LIFE_H

And the implementation of the member functions:

    /****************************************************************************
    ** $Id: life.cpp,v 2.5 1998/06/16 11:39:33 warwick Exp $
    **
    ** Copyright (C) 1992-1998 Troll Tech AS.  All rights reserved.
    **
    ** This file is part of an example program for Qt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #include "life.h"

    #include <qpainter.h>
    #include <qdrawutil.h>
    #include <qcheckbox.h>
    #include <qevent.h>
    #include <qapplication.h>

    // The main game of life widget

    LifeWidget::LifeWidget( QWidget *parent, const char *name )
        : QFrame( parent, name )
    {
        maxi = maxj = 50;
        setMinimumSize( MINSIZE * SCALE + 2 * BORDER,
                       MINSIZE * SCALE + 2 * BORDER );
        setMaximumSize( MAXSIZE * SCALE + 2 * BORDER,
                       MAXSIZE * SCALE + 2 * BORDER );
        setSizeIncrement( SCALE, SCALE);

        clear();
        resize( maxi * SCALE + 2 * BORDER , maxj * SCALE + 2 * BORDER );

    }

    void LifeWidget::clear()
    {
        current = 0;
        for ( int t = 0; t < 2; t++ )
            for ( int i = 0; i < MAXSIZE + 2; i++ )
                for ( int j = 0; j < MAXSIZE + 2; j++ )
                    cells[t][i][j] = FALSE;

        repaint();
    }

    // We assume that the size will never be beyond the maximum size set
    // this is not in general true, but in practice it's good enough for
    // this program

    void LifeWidget::resizeEvent( QResizeEvent * e )
    {
        maxi = (e->size().width()  - 2 * BORDER) / SCALE;
        maxj = (e->size().height() - 2 * BORDER) / SCALE;
    }

    void LifeWidget::setPoint( int i, int j )
    {
        if ( i < 1 || i > maxi || j < 1 || j > maxi )
            return;
        cells[current][i][j] = TRUE;
        repaint( index2pos(i), index2pos(j), SCALE, SCALE, FALSE );
    }

    void LifeWidget::mouseHandle( const QPoint &pos )
    {
        int i = pos2index( pos.x() );
        int j = pos2index( pos.y() );
        setPoint( i, j );
    }

    void LifeWidget::mouseMoveEvent( QMouseEvent *e )
    {
        mouseHandle( e->pos() );
    }

    void LifeWidget::mousePressEvent( QMouseEvent *e )
    {
        if ( e->button() == LeftButton )
            mouseHandle( e->pos() );
    }

    void LifeWidget::nextGeneration()
    {
        for ( int i = 1; i <= MAXSIZE; i++ ) {
            for ( int j = 1; j <= MAXSIZE; j++ ) {
                int t = cells[current][i - 1][j - 1]
                + cells[current][i - 1][j]
                + cells[current][i - 1][j + 1]
                + cells[current][i][j - 1]
                + cells[current][i][j + 1]
                + cells[current][i + 1][j - 1]
                + cells[current][i + 1][j]
                + cells[current][i + 1][j + 1];

                cells[!current][i][j] = ( t == 3 ||
                                          t == 2 && cells[current][i][j] );
            }
        }
        current = !current;
        repaint( FALSE );           // repaint without erase
    }

    //
    // Normally you implement drawContents() instead since LifeWidget
    // inherits QFrame.
    //

    void LifeWidget::paintEvent( QPaintEvent * e )
    {
        int starti = pos2index( e->rect().left() );
        int stopi  = pos2index( e->rect().right() );
        int startj = pos2index( e->rect().top() );
        int stopj  = pos2index( e->rect().bottom() );

        if (stopi > maxi)
            stopi = maxi;
        if (stopj > maxj)
            stopj = maxj;

        QPainter paint( this );
        for ( int i = starti; i <= stopi; i++ ) {
            for ( int j = startj; j <= stopj; j++ ) {
                if ( cells[current][i][j] )
                    // could avoid this if cells[!current][i][j] and this
                    // is a repaint(FALSE)... probably not worth it
                    qDrawShadePanel( &paint, index2pos( i ), index2pos( j ),
                                     SCALE - 1, SCALE - 1, colorGroup() );
                else if ( cells[!current][i][j] )
                    paint.eraseRect( index2pos( i ), index2pos( j ),
                                     SCALE - 1, SCALE - 1);
            }
        }
        drawFrame( &paint );
    }